Fix subtle incoming set bug.
Fix subtle handle compare bug.
This is the bug fix, not the last one.

The previous commit was probably healthy to to, but this is the one
that fixes the actual bug. Aiiieee.
iMinor tweaks to avoid excess copying.
Change incoming set to vector
Convert IncomingSet to HandleSeq

It's faster, avoids copying, since we only ever back_insert and
iterate, never delete nor random access.